Job Order (Seiban) Management System Implementation in Thailand

“We don’t know the real cost of each job until the month-end close. The only thing we can see is material cost; labor hours and subcontracting costs are buried in departmental expenses.” We hear this often from managing directors, plant managers, production control managers and cost accountants at Japanese-affiliated makers of automation equipment and special-purpose machines, jigs and inspection equipment, and molds and dies, as well as sheet metal and fabrication shops and conveyor line builders in Chonburi, Rayong, Ayutthaya and the Bangkok area. This article walks through implementing a job order (seiban) management system step by step, from how to number jobs to linking labor hours and connecting to accounting. (A “seiban” is a production job number: one number assigned to each customer order and used to track everything made for it.)

Here is the conclusion up front. A seiban management system is not “a system for putting numbers on orders.” It is a system for attaching three kinds of actual cost (material, subcontracting and labor) and progress to that number at the moment they occur. Whether implementation succeeds depends less on how clean the screens look or how many features there are, and more on who on the shop floor enters which seiban, and at what moment.

The three key points of this article are:

• Line up estimated and actual cost by element: material, subcontracting and labor (even if material cost is charged to the seiban, most overruns show up in labor and subcontracting)
• Raise the rate at which labor hours are linked to a seiban (when about one-third of the month’s direct labor hours are not tied to any seiban, job-level profit and loss cannot be trusted)
• Cost by seiban also feeds into how progress is measured for accounting purposes (when progress is measured on a cost-to-cost basis, missing links translate directly into understated revenue)

Note that all figures for “Model Plant C” in this article, including the number of seiban, costs, labor hours and labor rates, are original model settings and assumed values created for this article. They are neither industry averages nor survey results. Please read them as a “calculation template” to be replaced with your own numbers.

Why job-level profitability matters in 2026

Output is growing, but sentiment is weak

First, let us look at where Thai manufacturing stands. According to Thai Post (September 30, 2026), Thailand’s Manufacturing Production Index (MPI) for August 2026 was 103.43, up 4.44% year on year. The capacity utilization rate was 58.28%. The same report says the full-year outlook was also revised upward.

Business sentiment, on the other hand, is not strong. As reported by Thai Post (September 9, 2026), the Thai Industries Sentiment Index (TISI) of the Federation of Thai Industries (FTI) fell to 89.70 in August 2026 from 90.0 in July. The three-month outlook index was 97.0. Factors cited as weighing on sentiment include higher prices for energy and petrochemical feedstocks, a shrinking auto market (cumulative sales over 7 months down 17.38%), US tariffs and the situation in the Middle East.

Investment in equipment renewal and automation continues

On the capital investment side, activity is brisk. According to Thailand Business News (July 23, 2026, reporting based on a BOI announcement), applications for BOI investment promotion in the first half of 2026 totaled 1,299 projects worth US$43.6 billion, up 37% year on year. By sector, machinery, automation and robotics accounted for US$387.4 million (82 projects). By country of foreign direct investment applications, Japan ranked 5th with US$970.1 million (123 projects).

In addition, according to MGR Online (August 13, 2026), the BOI Secretary-General said that from 2023 through the first half of 2026, companies with Japanese shareholders filed more than 400 applications for investment promotion, with investment exceeding 55 billion baht. These reportedly include machinery upgrades to improve production efficiency.

Japanese companies in Thailand name rising material costs as their top issue

In the business sentiment survey for the first half of 2026 published on June 30, 2026 by the Japanese Chamber of Commerce, Bangkok (JCC) (504 respondent companies), the overall business sentiment DI moved from 0 in the second half of 2025 to −6 (estimate) in the first half of 2026 and −7 (outlook) in the second half of 2026, indicating continued deterioration. The DI for general machinery was −4 in the second half of 2025, 8 in the first half of 2026 and −12 in the second half of 2026. However, there were only about 20 respondents in general machinery, and the report itself notes that questions with few responses are best not assessed on percentages alone.

The top management issue was “rising prices of raw materials and parts,” at 65%. For the content of capital investment in 2026 (multiple answers allowed), renewal was 59%, rationalization 31% and DX-related 22%.

Order-takers need to know the profitability of each job sooner

From here on, this is our own reading. Investment in equipment renewal and automation is continuing. For companies that build special-purpose machines, jigs, inspection equipment and conveyor lines, that means order opportunities are continuing. At the same time, with high material costs and worsening sentiment, the profit built in at the quotation stage is easily eroded by rising material prices and growing adjustment hours.

Even if orders keep coming, if the profitability of each job is known only after delivery, there is no way to act on loss-making jobs. We think equipment and jig makers have a growing need to grasp the cost and progress of each job sooner.

What is seiban management? Seiban vs MRP and when to use each

Defining seiban management

What is seiban management? An exam explanation for Japan’s SME management consultant qualification (STUDYing) describes the seiban control method as “a method in which, when a manufacturing order is issued, instructions for all processing and assembly related to that product are prepared, and each is given the same manufacturing number for control.” MONOist (ITmedia, 2020) also describes it as a method of managing a product consistently under the same seiban, from raw materials to the final process.

A general explanation (Business Concierge powered by Onamae.com) describes it as a system that assigns a control number called a “seiban” to each order, and lists its advantages as easier progress tracking, lower inventory risk because procurement starts from the order, and the ability to track costs individually by seiban. As weaknesses, it lists a tendency toward parts shortages and excess inventory, and the effort required to assign and follow numbers.

Seiban vs MRP

According to the same explanation, MRP (material requirements planning) calculates requirements by part number and shares inventory of common parts across products. Seiban management, by contrast, assigns a number to each order and does not share inventory between products.

The table below organizes the explanation above, with practical perspectives added by the author.

Choose by ratio, not by which is “better”

Seiban management and MRP are not chosen on the basis of which one is better. The deciding factor is the ratio of order-specific items to common parts.

Take a special-purpose machine builder as an example. Frames, jig plates and dedicated machined parts are designed and ordered for that job only. Seiban management suits these. Common parts such as bolts, sensors, pneumatic components, motors and wiring, on the other hand, use the same part numbers across many jobs. Ordering them separately for each seiban increases ordering work and loses the benefit of bulk purchasing. For these, it is more realistic to hold stock via MRP or reorder points and attach the seiban when the parts are issued.

In other words, at many make-to-order plants a combination comes naturally: seiban-specific items under seiban management, and common parts stocked via MRP and charged to the seiban when issued. As a product example, TPiCS-X (TPiCS Laboratory) states that it supports production that combines seiban management and MRP. Which method to use, and how far, needs to be decided by looking at your own parts structure. If you use the MRP side, accurate item masters and bills of materials are a prerequisite. We cover this in detail in our article on MRP and master data accuracy. For the overall approach to production management in make-to-order manufacturing, see also our article on make-to-order production management.

Common problems in make-to-order manufacturing

Product vendors start from the same problems. OBC (Obic Business Consultants), introducing “TECHS-S,” its Bugyo Solutions offering for make-to-order manufacturing, lists as one problem of make-to-order production that “accurate cost per job cannot be grasped quickly, delaying the identification of and response to unprofitable jobs.” CIM Research Institute says its “Dr. Kotei Navi” series for make-to-order production, launched in April 2026, visualizes progress, delivery dates and cost on a large Gantt chart, and had announced that a purchasing option covering everything from ordering to receiving inspection was scheduled for release in July 2026.

These are cited as examples of functionality, not as recommendations of any particular product. Before choosing a product, the first step is to decide which costs your company will charge to the seiban, when, and through whose input.

Lining up estimated and actual cost by element for one seiban

Assumptions for Model Plant C

From here, we use Model Plant C. The assumptions are as follows (all are model settings for this article).

• A Japanese-affiliated maker of automation equipment and special-purpose machines in Chonburi Province, Thailand. About 80 employees, of whom 40 are direct workers
• About 120 seiban received per year (special-purpose machines, assembly jigs, inspection equipment, modification work)
• The order ledger and quotations are managed in Excel. Material purchase orders are entered into the accounting system with a seiban
• Labor hours are written in paper daily reports, but are only totaled by department. Subcontracting costs are booked together as departmental expenses at month-end
• Job-level profit and loss is estimated manually by the accounting team after delivery
• The labor cost allocation rate is 600 baht per hour

In what TOMAS TECH has seen, this situation is not unusual. Because material cost alone carries a seiban, people tend to believe that “seiban management is already in place.”

Estimate vs actual for seiban C-2604

Seiban C-2604 at Model Plant C is a job for one automatic assembly machine, with an order value of 3,000,000 baht. Lining up estimated and actual cost by element gives the following (unit: baht).

At the quotation stage, the planned gross profit was 600,000 baht (20%). In reality, costs overran by 290,000 baht and gross profit came to only 310,000 baht (about 10%).

Only the material variance was visible before delivery

The problem is less the size of the overrun than when the overrun became visible. Under the current setup, materials are ordered with a seiban, so the material variance of 60,000 baht was visible before delivery. Subcontracting costs, however, are booked together as departmental expenses at month-end, and labor hours remain only in departmental daily reports. As a result, of the 290,000 baht overrun, 230,000 baht (subcontracting 80,000 baht plus labor 150,000 baht, about 79%) became visible only after the close.

Put another way, when only material cost is charged to the seiban, the job proceeds with nearly 80% of the overrun out of sight. Material variances can be anticipated to some extent by buyers as price increases. Labor and subcontracting overruns, on the other hand, build up little by little every day on the assembly and adjustment floor. Only by lining up estimate and actual by element can you see where profit was eroded.

Breaking down the 250-hour labor overrun

The 250-hour labor overrun behind the labor cost overrun breaks down by type of work as follows (model).

Of this, the 70 hours (42,000 baht) spent responding to design changes are costs that could possibly have been billed to the customer as extras. But if those hours are not attached to the seiban, there is no record of when, who, and how many hours were spent on which change. Without a record, there is no basis for an additional charge either. Recording design changes and additional work under seiban sub-numbers is not only about capturing cost correctly; it also preserves the basis for billing.

The 140 hours of adjustment and rework are information that can improve the next quotation and design. The 40 hours of waiting for customer witness inspections are a prompt to review how schedules are arranged. None of this can be seen unless labor hours are attached to both the seiban and the type of work. We also cover how to connect estimates and actuals in our article on manufacturing CPQ (from quote to production).

Raising the rate of labor hours linked to a seiban

Where 9,600 hours a month go

Next, let us look at labor hours for the whole plant. Model Plant C has 40 direct workers; at 240 hours per person per month, monthly direct labor hours total 9,600. The breakdown, current versus the 90-day target, is as follows.

Currently, 3,360 hours (35%) are not attached to any seiban, about one-third of monthly direct labor hours. Of these, the 1,440 hours of indirect work are recorded with indirect codes, so we know what they were spent on. The problem is the 1,920 hours that are “unrecorded or unknown.” Multiplied by 600 baht, that comes to 1,152,000 baht: this much labor cost every month does not become the cost of any job.

If you produce job-level profit and loss in this state, every seiban looks cheaper than it really is. The accounting team can allocate departmental hours after the fact, but allocation averages out, and erases, the very information you most want: which jobs are losing money.

The goal is not to “charge everything to a seiban”

Note that the goal is not to “attach every hour to a seiban.” Indirect work such as setup, cleaning, training and meetings should be recorded honestly with indirect codes. Forcing indirect work into a seiban inflates the cost of whichever job happened to be worked on that day, and actually distorts job-level cost.

Model Plant C’s 90-day target is 8,160 hours (85%) of work linked to a seiban, 1,440 hours (15%) of indirect work and 0 hours unrecorded or unknown. Indirect hours do not change. The assumption is that the 1,920 hours that were “unrecorded or unknown” become attached to a seiban. This is a target set for the model plant; it does not mean that every plant can achieve these numbers.

Three reasons the linkage rate does not rise

In many cases, the reason labor hours do not get linked to a seiban lies not in system features but in how input is designed.

• Input is too late: A whole day is written at once in a paper daily report, and a clerk transcribes it into Excel at month-end. Memory is already vague at the time of writing, and miswritten seiban increase during transcription
• The seiban does not reach the floor: The seiban is not printed prominently on work instructions or drawings, so workers do not know which seiban their work belongs to
• There is no place for indirect time: There is no list of indirect codes, so time that cannot be attached to a seiban is left blank. Blanks become “unrecorded or unknown”

The countermeasures are the reverse of each. At the moment work starts and ends, scan the barcode or QR code on the work instruction or traveler tag with a tablet or smartphone. Print the seiban large on work instructions. Make indirect codes a short list with few items and post it in the work area. Explain things to workers in Thai, and make the screens Thai as well. None of this is expensive, but unless all of it is in place, the linkage rate will not rise whatever system you install. For designing how results are collected at each process, our article on process management systems may also help.

Cost by seiban, measure of progress and revenue recognition

Japan’s Cost Accounting Standards and the seiban

Cost by seiban is not just for internal control within the plant. It is also directly connected to accounting.

Section 31 of Japan’s Cost Accounting Standards (Genka Keisan Kijun, issued in 1962 (Showa 37) by the Business Accounting Council of the then Ministry of Finance) provides that job order costing applies to forms of production in which different kinds of products are produced individually, and that direct and indirect costs are accumulated for each specific production order (a summary based on the text reproduced on Wikibooks). In our view, it is natural to treat the seiban as the unit of this “specific production order.” However, the Standards do not state that “a seiban equals a specific production order.”

Revenue recognized over time and measure of progress

The other point of contact is revenue recognition. Paragraph 35 of IFRS 15 (International Financial Reporting Standards) provides that, for performance obligations that meet certain criteria, revenue is recognized over time. One of the criteria (paragraph 35(c)) is that the entity’s performance does not create an asset with an alternative use to the entity, and the entity has an enforceable right to payment for performance completed to date. In our view, special-purpose machines built to customer specifications are a type of contract where whether they meet this criterion tends to become a point of discussion.

When revenue is recognized over time, paragraph 39 of IFRS 15 provides that revenue is recognized by measuring progress, and paragraph 41 states that methods of measuring progress include output methods and input methods. For input methods, B18 gives examples such as resources consumed, labor hours expended, costs incurred, time elapsed and machine hours used. The method of taking costs incurred divided by estimated total costs as the measure of progress is generally called the cost-to-cost method.

Missing links mean understated revenue

Consider seiban C-2611 at Model Plant C: a complete conveyor line with a contract value of 12,000,000 baht and estimated total cost of 9,600,000 baht, spanning two accounting periods. We compare the situation at period-end in two cases (unit: baht).

When correctly linked, the measure of progress is 4,800,000 ÷ 9,600,000 = 50.0%, and revenue is 12,000,000 × 50.0% = 6,000,000 baht. On the other hand, if 400,000 baht of labor cost (about 670 hours when divided by 600 baht) gets lost in other seiban or indirect work, costs incurred become 4,400,000 baht, the measure of progress about 45.8%, and revenue 5,500,000 baht.

A cost leak of 400,000 baht has become an understatement of revenue of 500,000 baht. This is because the cost leak, multiplied by the ratio of contract value to estimated total cost (12,000,000 ÷ 9,600,000 = 1.25 times), flows through to revenue. Conversely, if another job’s hours are wrongly charged to this seiban, revenue is overstated. When progress is measured on a cost-to-cost basis, the accuracy of labor-hour linkage directly determines the accuracy of revenue.

Errors in the other direction: rework and purchased items before installation

The opposite of missing links is an error where the measure of progress comes out higher than reality. B19 of IFRS 15 states that, under a cost-based input method, an adjustment to the measure of progress may be required for costs of significant inefficiencies not reflected in the contract price (such as unexpected wasted materials or labor) and for costs not proportionate to progress (for example, purchased items whose control passes to the customer but which are installed later).

In other words, if large rework costs or the costs of expensive purchased items not yet installed are included as-is in costs incurred, the measure of progress may come out higher than reality. To tell these apart, you need to be able to identify, within cost by seiban, the hours and materials for rework and spoilage, and purchased items before installation, separately. This is why the checklist includes a record of rework and spoilage.

When progress cannot be reasonably measured

Paragraph 44 of IFRS 15 provides that revenue is recognized over time only if progress can be reasonably measured, and that progress cannot be reasonably measured if the reliable information needed to apply an appropriate method is lacking. Paragraph 45 provides that when the outcome cannot be reasonably measured, such as in the early stages of a contract, but the entity expects to recover the costs incurred, revenue is recognized only to the extent of costs incurred until the outcome can be reasonably measured. In our interpretation, if actual cost by seiban cannot be accumulated in a reliable form, there is a risk that this “reliable information” may be judged to be lacking.

Confirm application in Thailand with your audit firm or accountant

In Thailand, TFRS 15, the equivalent of IFRS 15, applies to publicly accountable entities such as listed companies, and many unlisted companies may use a different standard (TFRS for NPAEs). Many Japanese subsidiaries in Thailand appear to be unlisted companies, and TFRS 15 does not necessarily apply to them as is.

On the other hand, according to explanations by Forvis Mazars and FlowAccount, even under TFRS for NPAEs there are situations, such as construction contracts, where progress is measured as “cumulative costs incurred ÷ estimated total costs.” Whatever the standard, when progress is measured on a cost-to-cost basis, actual cost by seiban can serve as the foundation.

However, whether your contracts qualify for revenue recognition over time, and under which standard and method progress is measured, depend on the terms of each contract. Be sure to confirm individually with your audit firm or accountant. The calculations in this article are a model to explain the effect of the mechanism and do not represent a judgment on accounting treatment.

12 items to hold for each seiban (checklist)

Before choosing a seiban management system, decide what information to hold for each seiban. The following 12 items are a framework TOMAS TECH often uses at make-to-order plants.

1. Seiban: numbering rules (year, serial number, sub-number). Use sub-numbers to separate additional work, design changes and remakes
2. Customer, order number, contract value, delivery date: both the values at order receipt and the values after changes
3. Estimated cost: amounts by element (material, subcontracting, labor) and the revision history (versions) of the estimate
4. Bill of materials (BOM) by seiban: distinction between standard part numbers and seiban-specific items, and the revision level for design changes
5. Material procurement and allocation: distinction between items ordered specifically for the seiban and items issued from common stock
6. Subcontract orders and acceptance: process, amount, acceptance date
7. Actual labor hours: worker, process, start and end times, distinction from indirect codes
8. Process progress: milestones for design, procurement, machining, assembly, adjustment, shipment, installation and acceptance
9. Records of design changes and additional work: requester, date, hours affected, whether an additional charge is made
10. Records of rework and spoilage: cause, hours, materials
11. Shipment, installation and customer acceptance: the date of each and a reference to the supporting documents
12. Accumulated actual cost and variance: variance against the estimate and expected gross profit (updated monthly)

Quite a few of these items can be held even in your current Excel order ledger. Items 1, 2, 3 and 11 can be started just by adding columns to the ledger. The difficult ones are items like 5, 6 and 7, which must be entered at the moment they occur. That is where the reason for introducing a system lies.

Seiban management system requirements and integration

Labor input: “at that moment, by scanning”

The most important element is labor-hour input. Use a method in which the seiban and process are read by barcode or QR code at the start and end of work. Tablets or smartphones are sufficient as devices. Transcribing paper daily reports at month-end lowers both the linkage rate and accuracy. Make the screens Thai, keep the choices few, and give priority to workers being able to enter data in a few seconds without hesitation.

Materials: combine with MRP

For seiban-specific items, make the seiban a mandatory entry at the time of ordering. For common parts, hold stock via MRP or reorder points and attach the seiban when the parts are issued. As long as issue records carry a seiban, material cost by seiban can be accumulated even when common parts are held in stock.

Subcontracting: make the seiban mandatory on purchase orders

Include the seiban as a mandatory field on subcontract purchase orders, and book the cost to the seiban at acceptance. If, as at Model Plant C, subcontracting is booked together as departmental expenses at month-end, subcontracting overruns become visible only after the close. The key is to charge the cost to the seiban at acceptance, without waiting for the subcontractor’s invoice to arrive.

Design changes: link to PLM and CAD through sub-numbers

For design changes, link the change number on the PLM or CAD side to the seiban sub-number. If post-change hours and materials are accumulated under the sub-number, they can be used both as the basis for additional charges and to improve estimating accuracy. Specific integration methods are covered in detail in our article on PLM and ERP integration for engineering changes.

Accounting: connect through sub-accounts or cost centers

Connect with the accounting system by treating the seiban as a sub-account or cost center, so that work-in-process (WIP) balances by seiban can be produced monthly. The total of WIP balances by seiban matching the WIP account in the books is the check that cost by seiban can be trusted. For cost management systems as a whole, see our article on cost management systems.

Visibility, permissions and audit

Make the estimate-versus-actual comparison, progress and expected gross profit for each seiban viewable weekly. For ways to display shop-floor progress on screen, our article on production progress monitors may be useful.

Also, put changes to estimated cost and contract value under an approval process and keep a history of changes. If estimated cost can be rewritten after the fact, the variance between estimate and actual loses its meaning. This history is also needed when explaining the basis for job-level profit and loss or the measure of progress to the parent company or auditors.

For deciding whether to use a package product or build a custom system, see our article on scratch-built vs package systems.

RFP and acceptance testing for seiban management system implementation

This section is not based on external statistics or public guidelines; it is a framework drawn from TOMAS TECH’s practical experience.

What to include in the RFP

Including at least the following items in the request for proposal (RFP) for a seiban management system makes vendor proposals easier to compare.

Example acceptance test criteria

In acceptance testing (FAT and SAT), check not whether features exist but that “input without a seiban cannot be made (or triggers a warning).” The criteria below are presented as a model.

Common points of failure in implementation are also summarized in our article on production management system implementation failures.

A 90-day plan for seiban management system implementation

Finally, using Model Plant C as an example, here is a 90-day plan.

Days 0–30: set the rules and take stock

Decide the seiban numbering rules and the definitions of the 12 items. At the same time, take stock of the seiban currently in progress and get a grasp of each one’s estimate, materials and subcontracting already ordered, and labor hours to date. Create the list of indirect codes at this stage as well.

Days 31–60: start labor scanning in two processes

Start scanned labor input in two processes, assembly and adjustment. Both are processes where labor overruns tend to occur and differences between seiban are large. Explain things to workers in Thai, and tell them that the reason for entering the seiban is not evaluation but making estimates accurate. At the same time, make the seiban mandatory on subcontract orders, and check the linkage rate weekly.

Days 61–90: roll out to all processes and reconcile with accounting

Extend labor scanning to all processes. Produce profit and loss and WIP balances by seiban monthly and reconcile them with accounting. Start a meeting to review variances between estimate and actual, and for seiban with large variances, trace the causes back to the breakdown of labor hours.

Targets after 90 days

The targets set for Model Plant C are a labor-hour linkage rate of 85%, 0% unrecorded or unknown, and presenting profit and loss by seiban within 5 business days after the monthly close. These are targets for the model plant and are not a promise that any plant can achieve them in the same period.

Frequently asked questions (FAQ)

What is seiban management? How does it differ from lot control and MRP?

Seiban management is a method that assigns a control number called a seiban to each order and manages the processing and assembly instructions, materials, labor hours and subcontracting for that product under the same number. MRP calculates requirements by part number and shares inventory of common parts across products. Seiban management assigns a number to each order and does not share inventory between products. Lot control is an approach that tracks quality and history by units of product made together under the same conditions, and its purpose differs from seiban management, which tracks cost by order.

Should we choose seiban management or MRP? Can they be used together?

Think in terms of the ratio of order-specific items to common parts, not which is better. At many make-to-order plants, a realistic combination is seiban management for seiban-specific items, and stocking common parts via MRP or reorder points and attaching them to the seiban when issued.

In job costing for make-to-order manufacturing, how do we link labor hours to a seiban?

The basic method is to scan the barcode or QR code on the work instruction with a tablet or smartphone at the start and end of work, recording the seiban and process. Transcribing from paper daily reports at month-end lowers both the linkage rate and accuracy. Thai-language screens and input that takes only a few seconds are conditions for it to take hold.

Should indirect work and setup time also be charged to a seiban?

There is no need to force them onto a seiban. Record setup, cleaning, training, meetings and the like honestly with indirect codes. Forcing indirect work into a seiban inflates the cost of the job being worked on that day and distorts job-level cost. The aim is to eliminate unrecorded or unknown time.

Can cost by seiban be used for revenue recognition based on a measure of progress (cost-to-cost)?

As a general matter, under IFRS 15, when revenue is recognized over time, progress can be measured with an input method based on costs incurred, and actual cost by seiban can serve as its foundation. However, adjustments may be needed for costs of significant inefficiencies such as rework, and for the costs of purchased items before installation. In Thailand, many unlisted companies may use TFRS for NPAEs, and which standard applies differs from company to company. Be sure to confirm individually with your audit firm or accountant whether your contracts qualify for revenue recognition over time, and which method should be used to measure progress.

How long does seiban management system implementation take, and how should it proceed?

In this article’s model, the 90 days are divided into three stages. In the first 30 days, decide the numbering rules and the 12 items and take stock of seiban in progress; in the next 30 days, start labor scanning in two processes, assembly and adjustment; and in the last 30 days, roll out to all processes and reconcile with accounting. The actual period varies with the number of seiban, the method of integration with the accounting system and the scope of migration.

Summary

Implementing a seiban management system is not about putting numbers on orders. It is about building a mechanism that attaches three kinds of actual cost (material, subcontracting and labor) and progress to that number at the moment they occur, and success depends on who on the shop floor enters which seiban, and at what moment.

At this article’s Model Plant C, the cost of seiban C-2604 exceeded the estimate by 290,000 baht, and gross profit fell from 20% to about 10%. Of that, 230,000 baht (about 79%) was overruns in subcontracting and labor that became visible only after the close. Across the plant, 1,920 of the 9,600 monthly direct labor hours were unrecorded or unknown, and 1,152,000 baht of labor cost did not become the cost of any job. On jobs where progress is measured on a cost-to-cost basis, a cost leak of 400,000 baht leads to an understatement of revenue of 500,000 baht.

With investment in equipment renewal and automation continuing while high material costs and worsening sentiment overlap, we think the value for order-takers of knowing the profitability of each job sooner is increasing. A good place to start is comparing your current order ledger and daily reports against the 12 items in this article.

At TOMAS TECH, we are happy to talk even at the stage of keeping your current order ledger and daily reports and first trying to attach labor hours to a seiban in just one process. If you are struggling to grasp the cost or progress of each job, please feel free to contact us through our contact form.

References

• Business Concierge powered by Onamae.com (explanation of seiban management, updated November 20, 2025): https://www.onamae.com/business/article/33028/
• STUDYing SME Management Consultant course (explanation of FY2020 (Reiwa 2) Operations Management, Question 8): https://studying.jp/shindanshi/examarchive/unei_R2_8.html
• MONOist (What is process management? Back to basics, May 12, 2020): https://monoist.itmedia.co.jp/mn/articles/2005/13/news001_3.html
• IT Trend (TPiCS-X product page): https://it-trend.jp/production_management/1582
• Obic Business Consultants (Bugyo Solutions TECHS-S): https://www.obc.co.jp/solution/28
• Ipros Monozukuri (CIM Research Institute, Dr. Kotei Navi): https://pr.mono.ipros.com/cim/product/detail/2001619776/
• Wikibooks (Cost Accounting Standards): https://ja.wikibooks.org/wiki/原価計算基準
• Wikibooks (Job order costing): https://ja.wikibooks.org/wiki/個別原価計算
• EUR-Lex (Commission Regulation (EU) 2016/1905, IFRS 15): https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32016R1905
• Forvis Mazars Thailand (Construction contracts): https://www.forvismazars.com/th/en/insights/doing-business-in-thailand/accounting/construction-contracts
• FlowAccount (revenue recognition for construction contracts): https://flowaccount.com/blog/revenue-recognition-construction/
• Thai Post (MPI for August 2026, September 30, 2026): https://www.thaipost.net/economy-news/1079723/
• Thai Post (TISI for August 2026, September 9, 2026): https://www.thaipost.net/economy-news/1066384/
• Thailand Business News (BOI investment promotion applications in H1 2026, July 23, 2026): https://www.thailand-business-news.com/investment/321188-thailand-fdi-surges-37-to-43-6b-in-h1-2026-led-by-ai-data-centers
• MGR Online (meeting of BOI, JETRO and JCC, August 13, 2026): https://en.mgronline.com/culture/boi-joins-forces-with-jetro-and-japanese-chamber-of-commerce-to-accelerate-upgra/
• Japanese Chamber of Commerce, Bangkok (JCC) / JETRO (Survey on Business Sentiment of Japanese Corporations in Thailand for the 1st Half of 2026): https://www.jetro.go.jp/ext_images/thailand/pdf/JCCSurvey1H2026Eng.pdf